Bioactive peptides, which function as hormones, neurotransmitters and neuromodulators, and are thus vitally involved in virtually all cellular functions, are known to be generated from larger precursors via a variety of postranslational modifications. In particular, carboxyl terminus amidation is a key structural feature in the bioligical activity of many bioactive peptides. It is now clear that carboxyl-terminal amidation entails two sequential enzymtic steps. The first enzyme peptidylglycine a-amidating monoxygenase (PAM) catalyzes formation of the a-hydroxyglycine derivative of the glycine extended precursor. The second enzyme, peptidylamidoglycolate lyase (PGL) ---first reported by our laboratory--catalyzes dealdylation of the a- hydroxyglycine derevatives to produce the final amidated product plus glyoxylte. Our research program focuses on this carboxly-terminal amidation inhibitors, inactvator and substrate analogs and to delineate the role amidative processing in various cellular-level processes such as vascular function and tumor cell growth.